The accurate measurement of temperature is vital across a broad spectrum of human activities, including materials processing (e.g. making steel), manufacturing (e.g. parts only fit perfectly at a certain temperature), food (preparation, transport and storage), health, and of course scientific discovery. In fact, in almost every sector, temperature is one of the key parameters to be measured.
One difference between temperature and other physical properties, such as mass or length, is that it is intensive. If we consider two objects with the same mass and temperature, then their combined mass is the sum of the masses of the individual objects. However, their combined temperature will be unchanged. So, although it is fairly easy to imagine ways in which we can determine how much heavier one object is than a standard mass, it is not at all obvious how to determine how much hotter one thing is than another.
Temperature affects a wide variety of physical processes because all substances are composed of atoms, and fundamentally temperature is a measure of the average energy of the motion of the atoms within an object. The kelvin is defined in terms of this microscopic motion and is based on a fundamental constant known as the 'Boltzmann constant' that measures how much energy of motion corresponds to one kelvin.
This definition has that advantage that any fixed point can be used as a standard temperature, and any appropriate method for temperature measurement could be used. This allows for the possibility of improved uncertainty of temperature measurement at extremely high and extremely low temperatures.
NPL has a world leading team of researchers working in this area. We help organisations to understand the impact of reliable temperature and humidity measurement on their processes, solve their challenging measurement problems and enable innovative improvements in measurement techniques.
Temperature and humidity